1. Field of the Invention
The present invention relates to a method and an apparatus for processing an exhaust gas discharged from an internal combustion engine such as a diesel engine, in which fine particles (i.e. soot) trapped in a filter are removed outside of the filter so as to regenerate the filter and the removed fine particles are transported outside of an exhaust system and processed.
2. Related Art Statement
An exhaust gas discharged from a diesel engine includes a large number of fine particles mainly made of carbon, and thus this is a cause of a public nuisance generation. Therefore, various methods for trapping or eliminating such fine particles in an exhaust gas are disclosed.
For example, Japanese Patent Laid-Open Publication No. 1-159408 (JP-A-1-159408) discloses a method of removing fine particles trapped in a filter by using an intermittent counter flow and firing the removed fine particles in a re-trapping portion arranged in an exhaust gas passage near the filter. Moreover, Japanese Patent Application No. 5-198409 discloses a method of removing fine particles by using two kinds of counter flows, transporting the removed fine particles to a place remote from the filter and outside of the exhaust gas passage by the counter flow mentioned above, and firing the removed and transported fine particles.
However, in the method disclosed in JP-A-1-159408, since the re-trapping portion is arranged under the filter or in the exhaust gas passage near the filter, there is a possibility that the fine particles once removed by using the counter flow are returned to the filter by an exhaust gas.
Moreover, in the method disclosed in Japanese Patent Application No. 5-198409, since it is necessary to use two kinds of the counter flows, the apparatus for performing the method mentioned above is complicated. Further, since it is necessary to transport the removed fine particles to the place remote from the filter by using the counter flow, a large amount of the counter flow must be used. If the method mentioned above is used for an apparatus of processing an exhaust gas from an engine, it is preferred that an air supply source used for an exhaust brake system, for example, of the vehicle is used for a counter air supply source from the viewpoint of cost, size, etc. In this case, if a large amount of the counter air is used, it is necessary to make an actuator of the exhaust brake system large, and this causes a bad operation of the actuator.
It is an object of the present invention to eliminate the drawbacks mentioned above and to provide a method and an apparatus for processing an exhaust gas, in which, if fine particles are removed from a filter, transported by a counter flow and processed, the removed fine particles are not returned to the filter.
It is another object of the present invention to provide a method and an apparatus for processing an exhaust gas, in which fine particles can be removed, transported and processed effectively even by a small amount of the counter air.
It is another object of the present invention to provide a method and an apparatus for processing an exhaust gas, in which fine particles can be removed, transported and processed effectively by an apparatus having an simple constitution.
According to the invention, a method for processing an exhaust gas discharged from an internal combustion engine, in which fine particles trapped in a filter main body of a filter are removed by flowing an intermittent counter air, whose flowing direction is reversed to an exhaust gas flowing direction, through said filter main body, and the removed fine particles are transported outside of an exhaust gas system and are processed, comprises a first step in which an exhaust gas flow is stopped, and said counter air is supplied intermittently from a counter air discharge valve through a counter air supply pipe into a first counter room arranged at a downstream position of said filter main body; a second step in which fine particles trapped in said filter main body are removed by said counter air flowing through said filter main body; a third step in which said removed fine particles are transported to a second counter room arranged at an upstream position of said filter main body by said counter flow, and said transported fine particles are further transported to a process portion arranged at said second room and isolated from said exhaust gas flow; and a fourth step in which said transported fine particles are fired in said process portion.
Moreover, according to the invention, an apparatus for processing an exhaust gas discharged from an internal combustion engine, in which fine particles trapped in a filter main body of a filter are removed by flowing an intermittent counter air, whose flowing direction is reversed to an exhaust gas flowing direction, through said filter main body, and the removed fine particles are transported outside of an exhaust gas system and are processed, comprises a filter having a first counter room arranged at a downstream position of said filter main body and a second counter room arranged at an upstream position of said filter main body; an exhaust gas supply pipe for supplying said exhaust gas to said filter; an exhaust gas discharge pipe communicated from said first counter room to an outside; a process portion arranged at said second room and isolated from said exhaust gas flow, in which said removed fine particles are fired; a transport pipe, one end of which is connected to said second counter room and the other end of which is connected to said process portion; a counter air supply means for for supplying a counter air, whose flowing direction is reversed to said exhaust gas flowing direction, to said counter room; an exhaust gas supply valve arranged in said exhaust gas supply pipe; and an exhaust gas discharge valve arranged in said exhaust gas discharging pipe.